κόπτ' is imperfect (i.e. not an aorist) - should we interprete this as a repetitive action, "he hammered them against the ground like puppies"? The translations I looked seem to interprete this as single strike, but wouldn't that rather take an aorist? 'Hammered' is more vivid and a lot more gruesome, are they just playing down the violence to make Homer nicer?

I've always seen that as a repetitive, aggressive, action myself. Not a single strike but the full iterative function of the imperfect. Lifting, slamming, men screaming and trying to avoid violence even as Polyphemos breaks them etc.

I don't know if there's an attempt to tone down Homer, mayhap it just makes better English.